Various techniques are available for electrically and mechanically connecting one substrate with another substrate to form a semiconductor device. One technique includes placing leads or terminals on one face or side of a first substrate and coupling the first substrate with matching leads or terminals on one face or side of a second substrate. Frequently, bead-like projections or bumps are formed on the face of the first substrate which is then registered with matching terminals on the second substrate and the substrates are bonded together. Various types of semiconductor substrates such as diodes, transistors and integrated circuits may be formed with their terminals on one face or one side of the substrates. Such substrates are often referred to as flip-chips and the method of coupling two flip-chip substrates is frequently referred to as flip-chip bonding.
For several years hybrid solid state systems such as infrared detectors have been successfully incorporated into integrated circuits for mass production and miniaturization. Typically, such infrared detectors are fabricated with an N.times.M array of infrared detector elements or thermal sensors (sometimes referred to as a focal plane array). The focal plane array is generally bonded with an integrated circuit substrate to form the thermal imaging system. Bump bonding is a common technique used to couple a focal plane array with its associated integrated circuit substrate.
One procedure used in bump bonding a focal plane array with an integrated circuit substrate includes placing the integrated circuit substrate on a heated pedestal. The focal plane array is next placed in a gimbal and aligned with the integrated circuit substrate. Frequently, the gimbal is formed as part of a pivoting arm assembly. Linear motion may also be used to move the gimbal assembly. After alignment and registration of the focal plane array with the integrated circuit substrate, the assembly may be used to apply a pre-selected amount of force to the focal plane array and integrated circuit substrate. Heat may also be applied if required to aid in the bonding process. Typically such bonding is performed in either a vacuum environment or inert gas environment.
Prior bonding equipment and methods include the use of heat lamps, resistant heaters, heated and cooled lines, and thermoelectric means to obtain the required temperature profile depending upon the type of materials used in the bonding process. Likewise, gravity, load cells, air cylinders and diaphragms have been used to provide the necessary force during the bonding process.